Without the manual, most users cannot properly set the heat anticipator (if mechanical) or the cycle rate (if electronic), leading to temperature swings.
Mastering the Thermotech TT91 Temperature Controller: Ultimate Troubleshooting Guide for Heating Overruns thermotech tt91 manual hot
Power down the unit and use compressed air to blow out dust, lint, or manufacturing debris from the intake grilles. Without the manual, most users cannot properly set